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Topic: Born-Haber cycle  (Read 3118 times)

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Offline KitCh

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Born-Haber cycle
« on: December 05, 2009, 10:35:09 PM »
Why is the first answer positive and the second answer negative? Aren't they basically the same question?

1 - http://i48.tinypic.com/51ey41.jpg
2 - http://i49.tinypic.com/20aoqpu.jpg


 ???
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Offline UG

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Re: Born-Haber cycle
« Reply #1 on: December 05, 2009, 10:51:53 PM »
I think it's all down to definition really,
Some might define the lattice enthalpy as:
Na+ (g) + Cl- (g)  :rarrow: NaCl (s)  ΔlatH = -786 kJ mol-1
Or:
NaCl(s)  :rarrow: Na+ (g) + Cl-(g)  ΔlatH = 786 kJ mol-1
I think :-\ the latter is 'more correct'
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Offline KitCh

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Re: Born-Haber cycle
« Reply #2 on: December 05, 2009, 10:55:57 PM »
So Lattice Energy is always positive?
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Offline UG

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Re: Born-Haber cycle
« Reply #3 on: December 05, 2009, 10:58:13 PM »
:D Forget what I said before, I've just checked Wiki and it seems that the former is the one they use:

http://en.wikipedia.org/wiki/Lattice_energy
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